More of the nation's top billionaires live in the Big Apple than any other city, according to Forbes.

The magazine released its annual ranking of the 400 richest people in the U.S. Mondayand 53 New Yorkers made the list, having an average net worth of nearly $6 billion.

Last year's list had 46 NYC billionaires; their average net worth was merely $5.6 billion.

California, meanwhile, is the state with the most billionaires overall with 93.

An advocate who has fought New York City's income inequality says the list dramatically highlights the disparity between the Big Apple's rich and poor. It's "a dramatic expression that something is wrong with our system. People at the very top are doing better than ever before," said Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union.

Businessman David Koch was the top city resident, with a net worth of $42 billion, followed by former Mayor Michael Bloomberg, who recently returned to serve as CEO of his media company and has a net worth of $35 billion.

Other major New Yorkers on the list included Rupert Murdoch, who has a net worth of $14.2 billion, and Donald Trump, with a net worth of $4 billion. Joan Tisch was the only New York woman on the list. Her net worth is $3 billion.

None of the New York billionaires came close to the nation's richest man, Bill Gates, with a net worth of $81 billion.

Forbes' ranking arrives weeks after census data found that the mean income for Manhattan's highest earners went up 9 percent in 2013 and the top 5 percent of Manhattanites made nearly 88 times more than the lower 20 percent of the population.

Applebaum said there must be a renewed focus on closing the income gap, through a raise in the minimum wage, better access to jobs and more.

"It's about enabling people who go to work each day to be able to make enough to survive," he said.